The typical aircraft oil tank cap is an unhinged removable element that securely fits into the end of the neck of the tank and comprises a circular body having a peripheral groove to receive an "O" ring that bears against the inner diameter of the neck of the tank. A rotating handle that has limited movement positions a plurality of lugs into complimentary recesses formed in a lip extending circumferentially around the inner diameter of the neck. The lugs are spring loaded and a cam on the handle serves to position the lugs axially. Hence by lifting up the handle the lugs are freed from the lip and rotation thereof aligns the lugs with the recess to remove the cap and hence providing access into the tank.
This heretofore type or cap was susceptible of being left off the tank or improperly secured resulting in adverse consequences. For example, the handle of the cap could be in the secured position and to the eye of an inspector thereof, it would look secured. But while appearing to the eye to be secured, it merely would be loosely fitted and obviously could fall out of the neck allowing oil to escape.
Additionally, if the cap was not inserted properly, that is parallel to the wall of the neck, the "O" ring could twist or become distorted leading to excessive wear and/or inhibiting its sealing function.
I have found that I can obviate the problems noted above by providing a double hinge arrangement that retains the cap in proximity to the neck and restrains its motion in the opening and closing positions to a slightly axial motion that guides the cap parallel to the wall of the tank's neck. The tank locking mechanism carries a generally L-shaped handle that serves to lift and rotate a center rod for positioning the lugs into and out of the recess for locking the cap to the inner lip. A plate-like cam mounted adjacent the hinge cooperates with a lever extending from the handle prevents the handle from rotating except when the cap is in the closure position. The handle can then be rotated horizontally moving the lugs behind the lip and then rotated vertically to urge the lug toward the body of the cap, locking it into place.
The handle also serves to prevent the access door on the aircraft from closure until the cap is secured into position. Extension levers from the handle and the top of the cap are provided to assure blockage of the access door irrespective of the handle's location when it is in the unsecured position, whether it is in or spaced away from the tank's neck.